1. Field of the Invention
The present invention relates to an actuator, and more particularly to a synchronous actuator.
2. Description of the Prior Art
The use of actuators is quite extensive, and one kind of the actuators is the nonsynchronous actuator. Referring to FIG. 1, a conventional nonsynchronous actuator 10 comprises a base 11, a first cylinder 12, a second cylinder 13, a third cylinder 14, a motor 15, a first screw 16, a second screw 17 and a third screw 18. The first cylinder 12 includes a containing space 121, and one end of the first cylinder 12 is fixed to a top side of the base 11. The second cylinder 13 includes a containing space 131 and is pivotally disposed in the containing space 121 of the first cylinder 12. The third cylinder 14 includes a containing space 141 and is pivotally disposed in the containing space 131 of the second cylinder 13. The motor 15 is fixed to one end of the third cylinder 14. The first screw 16 is a hollow member and is defined with outer threads 161, and one end of the first screw 16 is fixed to the top side of the base 11. The second screw 17 is a hollow member and is defined with first inner threads 171 and second inner threads 172 that are threaded with the outer threads 161 of the first screw 16. One end of the second screw 17 is assembled to the open end of the containing space 131 of the second cylinder 13, and the other end of the second screw 17 is assembled to the open end of the containing space 141 of the third cylinder 14. The third screw 18 is a hollow member and is defined with first outer threads 181 that are threaded with the first inner threads 171 of the second screw 17. And one end of the third screw 18 is dynamically connected to the motor 15.
Referring to FIG. 2, during the operation of the nonsynchronous actuator 10, the motor 15 rotates the third screw 18 and drives it to move along the second screw 17, so as to drive the third cylinder 14 to move. When the third screw 18 rotates to the maximum length position relative to the second screw 17 as shown in FIG. 3, the third screw 18 will be driven by the motor 15 to rotate the second screw 17, and the second screw 17 will move along the first screw 16 and drive the second cylinder 13 to move. However, the above-mentioned conventional nonsynchronous actuator still has the following disadvantages:
Firstly, the extending and retracting motion of the conventional nonsynchronous actuator takes a lot of time, since the second cylinder 13 can be driven to move only when the third cylinder 14 moves to the end of maximum travel length.
Secondly, the components of the conventional nonsynchronous actuator are likely to be damaged, since the second screw 17 can be driven to rotate only when the third screw 18 rotates to the end of maximum travel length.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.